Reports for an extension to a listed building
Two consents, one evidence base. The heritage assessment has to describe significance before the design exists, and recording is expected where fabric is lost.
An extension to a listed building needs two consents: planning permission for the development and listed building consent for works affecting the building's character as one of special architectural or historic interest. They are applied for together, decided together and refused separately, and the listed building extension reports that support them are led by one document, an assessment of significance.
Section 16 of the Planning (Listed Buildings and Conservation Areas) Act 1990 requires the decision maker, in considering whether to grant listed building consent, to have special regard to the desirability of preserving the building, its setting and any features of special architectural or historic interest it possesses. Section 66 applies the same duty to planning decisions affecting a listed building or its setting. Neither duty is a balancing exercise on its own, and both come before national policy is reached.
Two applications, one pack
The application forms differ, and listed building consent carries no fee, but the supporting documents are largely shared.
Expect to submit existing and proposed drawings at a proper scale, including plans, elevations and sections, a site location plan, a Heritage Statement covering significance and impact, and a Design and Access Statement, which is required for listed building consent applications regardless of scale.
Drawing quality carries more weight here than on an ordinary householder application. Conservation officers read sections. A proposal showing a junction between new and old work at 1:20, with the existing fabric distinguished from the new, answers questions that no amount of written justification will.
Significance comes before design
The order matters and it is the single most common failing.
National policy requires an applicant to describe the significance of any heritage asset affected, including any contribution made by setting, to a level of detail proportionate to the asset's importance and no more than is sufficient to understand the potential impact. That description has to exist before the design does, because it identifies what the design must not damage.
A significance assessment involves documentary research, usually including the list entry, historic maps, the local record office and any earlier applications, and a careful inspection of the building recording its phases, its plan form, its surviving joinery and finishes and its relationship to outbuildings and grounds. The list entry description is a starting point rather than a statement of what matters, and it is frequently brief or inaccurate about the interior.
Where the asset is early, complex or high graded, specialist input is worth the cost. Where it is a straightforward grade II house, a well-researched assessment by a competent author is usually sufficient.
What the Heritage Statement has to do
Four jobs, in sequence.
Describe the significance of the whole asset, by element, distinguishing what is of high, medium and little or no significance. A plan coloured by significance is worth pages of text.
Identify the effect of the proposal on each affected element, saying plainly where fabric is lost, where plan form is altered and where setting changes.
Place the resulting harm in the national policy categories and, where it is less than substantial, say where in the range it falls and why.
Set out the public benefits, which must be public, and address the optimum viable use where the building is redundant or at risk.
A statement that jumps straight to justification, without the significance work, reads as advocacy. Conservation officers see several a week.
Recording where fabric is lost
Where the works will remove or conceal historic fabric, the authority will usually expect a record made before the work happens, at a level matched to the significance of what is being lost and the amount of information at risk.
Levels run from a basic visual record through to a full analytical record with measured drawings and documentary research. Choosing the right one is a judgement covered in choosing a historic building recording level, and the relationship between the record and the justification is explained in recording against a heritage statement.
Recording is normally secured by condition rather than submitted with the application, but the level should be agreed in advance, because a condition requiring an unspecified level is a dispute waiting to happen. The report itself sits at Historic Building Recording.
Structural evidence for interventions
Removing a wall, forming an opening, underpinning or inserting a steel into a historic building raises two separate questions: whether the intervention is structurally sound, and whether it is acceptable in heritage terms.
A structural engineer with conservation experience answers the first, and their approach differs from ordinary practice. Historic buildings often perform in ways modern analysis does not capture, and the conservation-minded answer is usually the least intervention that works rather than the most efficient structural solution.
Where a structural case is used to justify loss of fabric, the evidence has to be specific. A general assertion that a wall is unsound will not carry a conservation officer, and the parallel reasoning in conservation areas is set out in structural justification for demolition in a conservation area.
Trees, setting and archaeology
Setting is part of significance, so an extension that changes how the building is seen or understood affects the asset even where it touches nothing.
Boundary walls, outbuildings, gate piers and historic planting within the curtilage may be listed with the building as curtilage structures, and works to them need consent. This catches people out on garden buildings and garage conversions.
Trees within the setting need a survey where they are affected, and ground disturbance near an early building raises the possibility of below-ground archaeology, which may need a desk-based archaeological assessment and, occasionally, a field evaluation before determination.
Pre-application advice is worth buying here
Most authorities charge for pre-application advice, and on a listed building it is one of the few planning fees that reliably pays for itself.
The conservation officer will tell you, before the design is committed, which elevations they will resist, whether the interior alterations are likely to be acceptable and what level of recording they expect. That information changes the design brief. Receiving it for the first time in a consultation response, eight weeks into an application, means either a withdrawal or a refusal.
Ask three questions at that stage. Which parts of the building carry the most significance. Is the principle of an extension in this position acceptable. What would you expect to see recorded. Everything else can follow from the answers.
What the conservation officer is looking for
- A significance assessment that identifies what matters, before the design.
- Drawings that show the junction between new and old at a readable scale.
- Honesty about harm, with the level identified rather than argued away.
- Reversibility, where the intervention can be reversed without further loss.
- A schedule of materials and details, including mortar mixes, joinery profiles and glazing.
- A record of what is being lost, at an agreed level.
- Public benefits stated as benefits rather than as the applicant's requirements.
Illustrative example, for method only. A grade II farmhouse takes a single-storey rear extension connected by a glazed link. The link lands on a 1970s brick outshot of no significance, so no historic fabric is lost at the junction. One historic window opening is reused as the doorway, with the frame retained and stored on site. The record is agreed at a level matched to the modest loss. The conservation officer supports it, and the planning case rests on the same evidence.
PlanScope drafts a significance-led Heritage Statement and the supporting documents from your site details, and flags where research or a specialist author is needed rather than filling the gap.
This is general guidance, not legal advice. Check the position with your local planning authority or a qualified professional before relying on it.
PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.
Frequently asked questions
Do I need both planning permission and listed building consent?
For an extension, almost always. Planning permission covers the development and listed building consent covers works affecting the building's special interest. They are separate applications decided together, and one can be granted while the other is refused. Listed building consent carries no application fee.
What must a Heritage Statement contain?
A description of the significance of the asset by element, including the contribution made by setting, the effect of the proposal on each affected element, the resulting level of harm placed in the national policy categories, and the public benefits relied on. The significance work comes first and shapes the design rather than justifying it.
Does the list entry describe everything that matters?
No. List entries vary in age and detail and are often brief or silent about interiors. The entry identifies the building and its grade, but the assessment of what is significant has to be made on inspection and research. Listing protects the whole building, including parts the entry does not mention.
Are garden walls and outbuildings covered?
Often, yes. Structures within the curtilage that predate the relevant statutory date and were in the same ownership can be treated as curtilage structures listed with the principal building, so works to walls, outbuildings and gate piers can need consent. Check the position before altering anything in the grounds.
When is building recording required?
Where works will remove or conceal historic fabric. The level is matched to the significance of what is lost and the information at risk, and it is normally secured by a condition requiring the record before work starts. Agree the level in advance rather than leaving the condition to specify it later.
Sources and further reading
This article is general guidance about the planning system in England and, where stated, the rest of the UK. It is not legal or professional advice. Check your local planning authority’s validation requirements and take professional advice for your specific site.